Vacuum packaging in heat sealable plastic bags is a conventional way of packaging food items such as whole fowl, cuts of meat, cheese bricks and the like for sale at retail. Vacuum packaging involves placing the food item in a heat sealable plastic bag and then communicating the bag to a partial vacuum to evacuate air from the bag and collapse it about the food item. The bag is heat sealed in its evacuated condition so the food item becomes encased in a generally air-free environment.
It also is customary to fabricate the bag from a heat shrinkable plastic film. After sealing, the bagged food item is immersed in hot water or otherwise exposed to heat to shrink the bag so it is tight about the food item. This makes the bag substantially wrinkle-free and enhances the appearance of the bagged article for retail sale.
Apparatus, as disclosed for example in U.S. Pat. No. 5,062,252, has been developed to automate the vacuum packaging operation. The apparatus as disclosed in this patent has a plurality of carriers arranged for movement along a closed path of travel. During the course of moving through its closed path of travel, an open bag containing the article to be packaged is placed on the carrier. Each carrier then merges with a vacuum chamber and a partial vacuum is created to evacuate the bag. Each carrier is provided with a mechanically operated clamp that relies on an over-center force exerted by coil springs to hold the clamp at either a full open or a full closed position. The clamp closes against the bag neck after evacuation to maintain the bag in an evacuated state when the vacuum chamber separates from the carrier. The path of travel followed by each carrier carries it to a heat sealing zone containing at least one heat sealer which operates to heat seal each bag. After heat sealing, the clamp is opened and the carrier is moved to a location where the bagged article is removed.
The vacuum packaging apparatus of the present invention employs the concept as disclosed in U.S. Pat. No. 5,062,252 of clamping the evacuated bag so heat sealing the evacuated bag can occur outside the vacuum chamber. However, the clamping arrangement is modified to permit the clamp structure to swing over the bagged product to a clamped position and eliminates the need for springs to hold the clamp at a full open or a full closed position. The present invention also provides a platen on the carrier for supporting the bagged product and has a means for elevating and lowering the platen to facilitate automatic removal of the article from the carrier after vacuum packaging.